22. Cyclophosphamide is a substrate for cytochromes 2B6, 2C9, 3A4 and 2C19. Patients must not have received any drug that is a moderate or strong inhibitor of 2B6, 2C9, 3A4, and 2C19 within 1 week prior to receiving cyclophosphamide dosing through 72 hours after cyclophosphamide dosing. Patients must not have received any drug that is a moderate or strong inducer of 3A4 within 2 weeks prior to cyclophosphamide dosing.